Recuperator construction



Sept. 13, 1932. F G, SCHWALBE 1,877,599

RECUPERATOR CONSTRUCTION Filed Jan. l0. 1951 4 Sheets-Sheet 1 :JM/vento;

' dumm Sept 13, 1932 F. G. scHwALBE RECUPERATOR CONSTRUCTION 4 Sheets-Sheet 2 Filed Jan. l0. 1931 ..Willr fui 51 Ecl 2.

gwuewoz. c/zame Eq L mg M RECUPERATOR CONSTRUCTION Filed Jan. 10. 1931 4 Sheets-Sheet 5 gva/venten @vm/ng 57 defe/1MM@ Sept. 13, 1932. F. G. scHwALBE 1,877,599

RECUPERATOR CONSTRUCTION Filed Jan. n1o. 1931 4 sheets-Sheet 4 H615 .JC/260%@ Patented Sept. 13, 1932 FRANZ G. scHWALBnjoF 'ron-Eno, oHIo RECUPERATOR CON'STRU'GTIO1\TlA Application filed January 10, `1931. Serial No. 507,791.-H

My invention has for its obj ect to provide a recuperator for furnaces in which high temperatures necessarily prevail, in keeping with the use to which' the furnace is put,

such as a. glass furnace. The invention has for its particular object toprovide` a recuperator construction which will transmit heated air,

which is caused to move throughpassageways by variations of pressure, which passageways will be immune. from distortion or cracking,

to a fuel mixinglocality oxidation of the fuel.

Another object of my invention is to provide baffles so interconnected with the passageways through which the heated air is conveyed as to support and apportion the weight of parts of the passageways to be borne by other parts of the passageway, .the

forms and constructions of which are adaptable to withstand these weights.

The invention consists in other features and advantages which will appear from the following description and upon examination of the drawings. Structures containing the invention may partake of different forms and may be varied to their details and stillembody the invention. To illustrate a particular application of the invention I have selected a' recuperator construction embodying the invention as anexample of the various structures and details of such structures that conta-inthe invention and shall describe the selected structure hereinafter, it being understood that variations may be made and that certain features of my invention may be used toadvantage without a corresponding use of other features and without departing from the spirit of the invention. The particular structure selected is shown in the ac- 10 companying drawings.

Fig. l illustrates a top view of the recupera-tor, a part of the top wall beingshown broken away. Fig. 2 illustrates a view taken on the plane ofthe line 2 2 indicated in Fig. l. Fig. 3' illustrates a view taken on the plane of the line 3 3 indicatedin Fig. l. Fig. 4 isa cross sectional view of one of the passageways or tube units ofthe recuperator. Fig. 5 illustrates al longitudinal section of one of the passageways or tube units of to insure proper' the recuperator. Fig. 6 illustrates a viewV of a part of the middle baffle ofthe recupera-V tor. Fig. 7 illustrates a view of Va part of other lof the baffles located in the recuperator.,l l In the operation of furnaces in .which high 5 temperatures are maintained, and inwhch it is necessary,` in orderto operate the furnace eiiicientlyand atv a low co-st, ltofmix with the fuel burned in the furnace certain quantities of heated air preparatory to the 60. ignition of the fuel, recuperators are provided toconvey theair to the mixing locali#V ties and to warm it enroute by the warm exhaust gases previously given o by the furnace. Heretofore, air has been conveyed to the mixing-v localities byy means `of Atubes formed of clay materials. `VThe tubes have been joined with one another by means Vof other plasticclaymaterials in al manner well known in the art. These tubes were located m so that the exhaust gases from the furnace, which are often of a temperature of approximately 2300 degrees F., impinge directly on the tubes to heat themr and consequently the air being conveyed therethrough. Because of this intense heat the clay tubesqwill'erode and often crack due to expansion and contraction, as likewise, will the material which serves to join them and the exhaust gases will enter through Vthe cracks into the tube and mix with the air which decreases the efficiency of the established mixing ratio of K' the air with the fuel, or the air. will escape from the tube through the cracks intothe exhaust gaschamber which likewisey disturbs the established mixing ratio. -The escape of air from the tubesthrough the cracks will be increasingly evident if the air passing through the tube is impressed by a blow fan or the "like, VCracking or breaking of thev tubes often causes an abandonmentvof opera.- tion of the furnace pending repairs or replacements. The cost of these periods of inactivity are relatively high and reduce` the cost efficiency ofthe furnace as aA whole. A furnace having a recuperator partaking of the advantages of my invention will not be subjected to periods of inactivity and of consequently increased overhead becauseV of cracking or breaking of the tubes within the '.100

recuperator.

tially heat insulated from each other' by a v the mixing localities or it are subjected chamber substantially lled with a heat transmissionally resistant material. The

outer tubular shell of the tube unit may be kformed of clay materials and theinner tubular shell may be formed of commercial `high temperature resistant, chrome iron metal tubing. in theother in aspaced relation so that the inner tubular shells will besubstantially surrounded by heat insulating` air. chambers. Consequently, the outer tubular shells which directly to the heat of the exhaust gases from the furnace at about 2300 degrees F. will transmit their heat by radiation to the inner tubular shells and through the insulatingrbody. The resistance to heat flow establishes a temperature gradient between the outer surface of the clay tube, or shell, and the inner surfaces of the clay shellV and also between the inner surface of the clay shell and the outer surfaceof the metalv tube,

or shell. Owing to the high conductivity of the metal tube, orV shell, there is very little temperature gradient between its outer and inner surface and consequentlyfthe temperature of the tube closely approximates that of the air which is being preheated which results in a temperature well withinva safe 'temperature range of the metal of the inner shells, or tubes. 'lhus, the inner tubular shells will not be subjected to distorting heat strains and cracks or openings will not-be formed therein through which the -air or gases may move and-the inner tube will not be moved relative to the outer tubedue to heat expansion, but will expand through the same `distances as the outer tube expands when the outer tube is subjected to exhaust gases. Thus, air may beblown through the inner tubular shells to may be caused to move by creation of a draft or suction, asby a chimney, through the inner tubular shells.

he recuperator shown for purpose of illustration has suitable walls which are supo ported on a flooring 4l and is covered by a suitable roof 6 tol form a chamber 7. The chamber 7 is divided into two compartments, an upper compartment S and a lower compartment 9, by a horizontally extending wall 10. The upper compartment 8 of the chamber 7 communicates with a furnace 111 through a passageway 11. A port 12 may be located in the walls 13 .of the passageway 11 through which the fuel may be introduced preparatoryto its ignition in the furnace lll. K Thus, the passageway 11 forms a mixing locality wherein the fuel and the heated air introduced from the upper compartment 8 of the A Y recuperator encompassingV the features of my invention, as herewith setk The tubular shells are held one witho from the furnace 14. The furnace is connected to the lower compartment 9 of the chamber A7 ythrough passageways- 15 which have openings 16'in the furnace 14e so as to withdraw theburnt gases through the passa-geways l5 and -into the lower compartment 9 of the chamber through openings 18 formed inthe chamber wall 5. The air which is being heated and conveyed to the upper compartment passes through a plurality of tube units 20. In order to withdraw the exhaust gases from the lower compartment 9 of the chamber 7 as they become cooled, openings 19Varellocated in the bottom portion lof the wall 5 and communicate with passageways 21, which are connected with a suitable staclr.Y Thus, it will be seen that the exhaust gases will be drawn about the tube units 2O to heat the air passing through the tube units and the gases then allowed to escape. Y 'e The tube units 20 are constructed so as to have outer tubular shells 25 formed of-short tubes 27 of clay material connected together and inner tubular shells 26 formed of metal tubing. rlhe tubular units 20 are located in the lower compartment 9 of the chamber 7 so asjto connect openings 30 formed inthe flooring 4 of the recuperator with openings Sl'formed in the partitioning wall 10'. rlhe openings 30Y and 31 are substantially of the same diameter as the external diameter of the inner tubular shells 26 which are readily insertable within the openings 30 and 31 to prevent escape-ofexhaust gases from the lower compartment9 ofthe chamber 7 through the openings. Each outer tubular shell 25 is located so as to surround the openings 8O and Stand is secured in position by suitable cementitious materials. ln order to support and locate the inner tubular shell 26 within the Youter tubular shell 25 so thata chamber 3l may be provided to contain a heat resistant element intermediate the 'walls of the tubular `shells,`a plurality of runners or strips 35 of angleiron may be suitably attached as by welding, to the outer` surface of the inner tubular shell 26 so as tov extend along the inner tubular shell. By reason of the knife-like edges of the strips which are in contact with the outer tubular shell 25, the conduction of heat from the outer tubular shell to the inner tubular shell will be low. The inner tubular shellV 26 is thus protected from the intense heat of the gases which would cause thermal expansion of the material of which the shell 26 is formed to an extent where it would be displaced from its'normal and installed position with reference to the shell 25 which is formed of a material having a low coefficient of thermal expansion.

quantity' or quality of the heat resistant element in the chamber may be varied to effect an equal thermal expansion of both the tubular shells when the outer shell is subjected to the heat of the exhaust gases. The heat transmitted to the shell of high thermal expansibility through the chamber 34 and the heat resistant element contained therein from the outer shell will beV of such degree as to cause a thermal expansion of the inner tube equal to the expansion of the outer tube. Thus, the inner tubular shell is located in a spaced relationship on the vinside of the outer tubular shell 26 and around which the exhaust gases of the furnace are caused to swirl.

To direct the exhaust gases so Vthat they will iinpinge on all the tube units 2O located in the lower compartment of the chamber a plurality of baffles 40 are located horizontally in the lower compartment of the chamber. The baiiles 40 may be formed of blocks 4l of clay materials which are resistant to high temperature and extend from and are supported by the walls 5 of the chamber. The baiiies 40 are connected to the outer tubular shell of the tube units 2O by blocks 41 which f Thus the baiiies 40 will be supported by theV outer tubular shells 25 and the Wall 5 and will serve to support portions of the outer tubular shells 25.

In order to apportion the weight and burden of the tubular shells 25 and also to provide an added baille, a platform 45 is provided. The platform 45 may be located substantially horizontally and centrally in the lower compartment of the chamber yand may be formed of blocks 46 of clay material resistant to heat. The platform 45 is located about the tube units 2O and spaces the tube units so as to allow exhaust gases to circulate between the tube units. The blocks 46 which surround the tube units 2O have inwardly rounded corners 47 which have a radius substantially the same as the radius of the outside surface of the inner tubular shell 26. A. collar 48 formed of angle iron may be secured to each inner tubular shell 26 for sustaining the bottom corner of the blocks 46.

Thus the weight of the short tubes 27 whichy form the upper part of the outer tubular shell 25 and which are built above the platform 45 willbe supported on the collars 48 by the inner tubular shell 26. The expansion, by reason of heat transmitted to the inner tubular shell 26 Vto which the collars 48 are connected' prevents separation of the short tubes 27 ,v

which form the outer shell, away from each other at the points of jointure of the tubesl 27 at which thecolumn of tubes 27 are con- Anected to the collar 48.- This feature of-construction lessens theweight borne Vby the short Y tubes27 .forming the lower half-of the `outer .tubular shells of "the tubeunits 20 and places part of thatnweightA on theinner tubular shells 26 in theopenings 30. jThe'y openings SOcOmmunicate with passageways 6l-'which may be vcontrolled by a suitabledamper.52..` Thedamper `52 will control theair passing through the passageways 5l and consequently through the opens mixing localities.

Inf order toprovide for a forced draft of l air through the-tube `units V20 and to decrease Y ings BO-and the inner tubularfshells 26 to the tubes or shells the operating temperature ofthe first row offr tubes at their upper endsya'number o f tube units may be connected together at their openingsy 80'by L l-shaped pipes 55. The air is introduced into the" tube units which are so which directsthe air through the pipes 56 and the pipe 57 which extends" into the vupper-compartment 8 of thechamber 7. The pipe 57 is connectedto one of each pair of tube units by a'series 0f teats 58 which substantial-1 ly iit the openings 8l Iin the wall 10. The openings 3l communicate withoneof each Apair of tubeunitsf20 as connected `together by the U-shapedpipe. .Thus theair may be driven downwardly `through one of the pair1V of joined tube units 20 through theV U-shaped pipe 55 and upwardly `through the second of the pair of joined tubeunits to the mixing locality. f Theamount of air being conveyed to the mixing locality may be easilyvvaried to maintain efficientl burning of the fuel by varying the volume of the air introduced in the tube units 20.`

`Iclaim:V

l. Inv alrecupe-rator having a plurality` of connected by means of a suitable lolowfan-y vertical tube units, eachtube unit comprising Y a tubular shell and a plurality of superimposed tubular shells o-f substantially the same diameterl and Iarranged 'coaxially with the first named tubular shell, mea-ns connected tothe lirst named ltubular shell for supportingthe weight of certain of the second named tubular shells and means for maintaining Vvthe walls of the inner and outer tubular shells in spaced relation to each other.

2. In a recuperator having a plurality of vertical tube units, each tube unit comprising a pair of concentrictubular shells, the Iouter Vsurface of the inner shell having longitudinally extending4 spacer stripsand `means for connecting the outer shell to the strips for supporting the weight of the vouter shell on the inner shell. Y M

3. In a recuperator having a plurality of verticalI tube units, each tube unit-comprising a tubular member and a plurality of superimposed shells of substantiallythe same diameter and arranged coaXiallyY with the tubular member, baile members extending horizontally with reference to the tube units, and metal strips extending parallel to the axes of the tubesv and located intermediate the l tubular-member and' the'shells for maintaining and supporting the shellsV in spaced relation to the tubular member and means for connecting the strips to the battle members for supporting the ba-iiie members.

1l. In a recuperator having a plurality of vertical tubevunits, each of the tube'units comprising la pair of concentric tubular shells, one of the said pair of shells formed of iired 4plastic earthen materials Vand the other of .said pair of vshells formed of metal, means `loca-ted intermediate the said pair of shells for locating the iirst named shell upon the second named shell vand for forming sealed chambers between the shells resistantd to the transmission of heat from one shell to the other.

5. In a recuperator having a pluralityof vertical tube units, each tube unit comprising` a tubularmember and a plurality of super# imposed tubular shells of substantially the same diameter and arranged coaXially with the tubular member, the tubular shells being j formed of fired earthen materials, means forL connecting the tubular member to the tubular shells for vsupporting the weight of portions of the tubular shells and for preventing the p said supported tubular shells from exerting a pressure on adjacent tubular shells to cause cracking and crumbling of the walls of the vtubular shells.

6. In a recuperator having a pluralityof tube units, each of the tube units comprising a pair of concentric tubular shells of difierfrom ywhich the other of the said pair ot ent diameter, oneV of said pair of shells formedv of a material having a c'oelicient of thermal expansion different from that of the material y tubular shells is formed, and spacer strips located between the tubular shells to form chambers resistant to heat transmission from one shell to another for effecting substantially equal thermal expansion of the shellsY upon application of heat to the shell formed of a material having the lower coefficient of expansion. A

7. In a recuperatorhaving a plurality of tube units, each of the tube units comprising a pair of concentric. tubular shells', means located between the shells for forming chambers resistant to the transmission of heat to control the thermal expansion of one of the said pair of shells upon application of heat to the other of the said pair of shells. Y

In witness whereof I have hereunto signed my name to vthis specification.

FRANZ G. SCHWALBE. 

